In a wireless communication system, a paging procedure is used to call a specific user equipment or a plurality of user equipments. Two kinds of paging messages, i.e., Paging Type 1 and Paging Type 2 are used in a universal mobile telecommunication system (UMTS).
The Paging Type 1 message is used to call a user equipment which is in an idle mode and a connected mode of CELL-PCH and URA_PCH. A core network can call a user equipment which is in an idle mode to set up signaling access to the user equipment or to request the user equipment of setup of call or session. Furthermore, the core network can call a user equipment which is in a state of CELL-PCH or URA_PCH so that the user equipment performs a cell update procedure or a URA (UTRAN Registration Area) update procedure. Also, UTRAN can use the Paging Type 1 message to command the user equipment to read updated system information. Since the updated system information is important for all user equipments within a cell, all user equipments within a cell can be called. To identify a user equipment which is to be called, a paging message includes identification information of a user equipment. If a user equipment is in an idle mode, the paging message includes identification information of an upper level, such as International Mobile Subscriber Identity (IMSI), Temporary Mobile, Subscriber Identity (TMSI), and Packet Temporary Mobile Subscriber Identity (P-TMSI). If a user equipment is in a connected mode, the paging message includes UTRAN radio network temporary identity (U-RNTI).
The Paging Type 2 message is used in case where the user equipment is in a connected mode of Cell_DCH or Cell FACH state. Also, the Paging Type 2 message is used to additionally call the user equipment through RRC connection which is previously set. Since the RRC connection is used for the Paging Type 2 message, a dedicated call of a specific user equipment can be implemented.
A user equipment which is in an idle mode and a connected mode of CELL_PCH and URA_PCH state in the UMTS supports a discontinuous reception (DRX) mode to reduce power consumption. The discontinuous reception mode means that a user equipment does not always monitor a specific channel to receive downlink data transmitted from a network but is in a sleep mode for most of the time and wakes up for a specific interval to identify the presence of data received from the network. When there is a call from the user equipment, the UTRAN transmits paging indication (PI) to the user equipment through a paging indication channel (PICH) to indicate that a paging message will be transmitted after a certain time period. The user equipment which has received PI receives the paging message after a certain time period.
As described above, in a universal mobile telecommunication system (UMTS), a user equipment which is in a connected mode of CELL-PCH or URA-PCH as well as a user equipment which is in an idle mode is operated in accordance with the DTX mode. However, in the related art, since a network calls a user equipment which is in an idle mode and a user equipment which is in a connected mode of CELL_PCH or URA_PCH by using the same paging channel, problems occur in that the paging channel is not suitable for features of the user equipments which are in respective states and radio resources cannot be used efficiently.